1. Field of the Invention
The present invention relates to a semiconductor light-emitting device and a method of fabricating the same. More particularly, this invention relates to a high-brightness semiconductor light-emitting diode (LED) using a III-V group compound semiconductor which emits light in a green region, and a method of fabricating the same.
2. Description of the Related Art
During the last few years, the advancement of the information processing technology increased the demand for LEDs as a light source for optical communications, optical recording media, display and so forth. Development of green-light emitting LEDs of a short wavelength among all LEDs is strongly demanded for higher information density.
Light emission in a range from yellow to infrared has been realized using materials, such as GaAs, GaP, GaAlAs and GaInAsP. The wavelength limit of light emitted is considered to be about 700 nm. In.sub.x Ga.sub.y Al.sub.1-x-y P (0.ltoreq.x, y.ltoreq.1; hereinafter may be referred to simply as InGaAlP) mixed crystal, which has a lattice matching with a GaAs substrate, is considered most promising as a material that has a band gap of about 1.9 to 2.4 eV with a direct transition type band structure and is expected to cause highly-efficient light emission. The use of such a mixed crystal semiconductor is effective in producing LEDs with a heterojunction structure and high light emission efficiency. In fabricating such LEDs which emit light of a short wavelength, since the band gap energy of the substrate is always smaller than energy of emitted light, the substrate absorbs most of the irradiated light, thus significantly reducing the brightness. The same can be said to when the substrate is located on the side of the non-light-emitting face. That is, light emitted from the light-emitting layer and entering the substrate is not effectively guided outside.
As described above, LEDs with InGaAlP, serving as a light-emitting layer, which has a large band gap suitable for green light emission, do not have a sufficient light outputting efficiency due to light absorbed by the substrate.